In recent years, development of the three-dimensional mounting technique of stacking chips in a longitudinal direction has advanced in association with device miniaturization and high integration, and the through-silicon-via (TSV) technique of penetrating a substrate to form electric connection in the vertical direction has been more important.
It has been demanded for such a TSV structure that the thickness of a TSV landing pad connected to a TSV is increased to prevent penetration of the TSV through the pad upon formation of the TSV. In response to such a demand, Japanese Unexamined Patent Publication No. 2015-79961 describes the technique of stacking two or more metal films to form a thick TSV landing pad.